Owing to their physical properties III-V nitride compound semiconductors having the structure In.sub.x Al.sub.y Ga.sub.1-x-y N(0.ltoreq.x, 0.ltoreq.y, x+y.ltoreq.1) are of major importance for optoelectronic applications. To fabricate such semiconductor layers of high crystalline quality as are required for optoelectronic applications, for example, various epitaxial processes are employed. In addition to molecular beam epitaxy, for the most part vapor-phase epitaxy and especially metal-organic vapor-phase epitaxy (MOVPE) are utilized. Here, the growing temperature, depending on the material system, is typically 700-1100.degree. C. To grow crystalline layers, a suitable substrate has to be used. Sapphire (Al.sub.2 O.sub.3) or silicon carbide (SiC) have proved to be suitable substrates for III-V nitride compound semiconductors having the structure In.sub.x Al.sub.y Ga.sub.1-x-y N (0.ltoreq.x, 0.ltoreq.y, x+y.ltoreq.1). As a substrate material, silicon carbide (SiC) is very expensive. Sapphire (Al.sub.2 O.sub.3) is not conductive and, owing to its mechanical hardness, very difficult to work. Where the substrate is not conductive, all contacts have to be applied on the front side of the components. This uses up additional, expensive epitaxy space.
Silicon is a very common and attractive substrate material. It is mechanically stable, inexpensive, available almost without restriction, temperature stabile and conductive. It would therefore make a generally desirable substrate for the above-mentioned compound semiconductors. From P. Kung et al, Appl. Phys. Lett 66, 2958 (1995) we know that silicon, in principle, is suitable for the deposition of crystalline AIN and GaN layers and their ternary and quaternary compound semiconductors. Yet the authors note that the AIN and GaN layers produced on a silicon substrate exhibit crystals of insufficient quality for the fabrication of electronic components.